I am not a consequentialist (which is one who would say extreme freedom/ no government works best, so is therefore good). The issue here is the core of the philosophy, which is “the ends justifies the means.” Even though they may reach the same conclusions in nearly every way when landing on extreme freedom, the second their assumed desirable end changes, they now feel morally right to do wrong.
Caring more about basic morality, I say extreme freedom/ no government is right, therefore is good.
Nonetheless, my very first exposure and steps toward anarchy stemmed from enjoying content from consequentialists. Voluntary trade incentivizes better quality and lower prices.
If I understood your ideal scenario, you already mention private defense groups. The groups who do the best work will get the most customers. If no one wants to pay for such a group or thinks they can best defend themselves, they simply do not pay for such a service or start their own service to compete with others. Those who offer poor performance, participate in non-ideal ways, or charge too much, aren’t guaranteed funding/ may go out of businesses.
Larger regional threats may simply instigate a coordination between various defense groups. There are theories that within an everything-privatized world, there may be larger regional defense groups who would coordinate with the smaller region defense groups, tipping structures for additional funding, insurance, etc. David Friedman is likely the most prominent speaker on that in particular.
I can support any and all methods of voluntary cooperation and organization such as listed, which do not infringe on individual rights. HOWEVER, in my view, the absolute *best defense* would actually stem merely from a large-scale understanding of self-ownership.
Imagine trying to conquer such a region, where you try to force these people to do anything. You may be able to get by with little success by brute violence, but it wouldn’t last long when the entire region knows you have no right to control them… they would disobey, undermine, and overthrow you at the drop of a hat. Brute violence alone to control others at such a scale would be too costly.
Now also add in their own privatized defense groups to this scenario and assume 80% are armed, themselves. Good luck trying to conquer or control such a group! It would likely be impossible for any real duration of time.
On that note, I’ll mention this has ALREADY HAPPENED! The people within the USA have been conquered and it’s by the ruling class who call themselves “your government.” The only real reason they successfully control everyone is because the masses feel an obligation to obey.

